The demolition shear (also called concrete shear or breaker shear) is a hydraulic attachment for excavators that crushes concrete, masonry, and reinforced concrete structures through compressive force. Two counter-moving shear jaws generate closing forces of 50 to over 300 tons and break concrete like a shear cutting wire.
Primary demolition shears (coarse crushing on the building) and secondary demolition shears (further crushing on the ground) are distinguished. Combo shears combine concrete breakers and scrap shears in one unit: one jaw side breaks concrete while the other cuts reinforcing steel. Leading manufacturers include Epiroc (formerly Atlas Copco), Darda, Genesis, and NPK.
For high-reach demolition, shears are mounted on longreach booms and operate at heights up to 40 meters. The shear must match the excavator weight: oversized shears on undersized excavators create stability problems. As a general rule: shear weight should not exceed 10-12% of the excavator's operating weight.